The practical application of the regulation of a distinguishable porcine blastomere to differentiate into the inner cell mass, hence the offspring, will be investigated. Porcine blastomeres will be obtained by microdissection of an 8-cell embryo recovered from a pure "red" breed and then intermingled with blastomeres of a 4-cell embryo recovered from a pure "white" breed. The development of the resulting chimaeric embryos will be monitored at term after in utero transplantation and after in utero transplantation following a temporary culture period in the oviduct of a porcine recipient. Fifty percent of the embryos cultured in oviducts will be protected with a 1.0% agar coating. Red piglets born are assumed to be twins originating from the 8-cell embryos. Other piglets born colored white or sandy will be recorded as pure "white" breed or a chimaeric piglet. 1/8 porcine blastomeres are expected to develop similar to 1/8 blastomeres of other species. Solving the technical problem of the requirements of development in vivo of 1/8 porcine blastomeres and their direction to result in a distinguishable offspring will definitely increase the practical use of embryo transfer in the commercial swine industry.